Typically, a CIS-based thin film solar cell has an integrated structure, in which a backside electrode layer formed on a substrate is divided by a dividing groove referred to as pattern 1 (P1) and a CIS-based light absorption layer (hereinafter referred to as “light absorption layer”) and transparent conductive film formed on the backside electrode layer are divided by dividing grooves referred to as pattern 2 (P2) and pattern 3 (P3), whereby a plurality of unit cells are connected in series.
In a prior art CIS-based thin film solar cell, a shunt path (20c) is formed through the light absorption layer between the adjacent regions of the backside electrode layer divided by pattern 1 (P1) and a leakage current flowing through the shunt path (20c) causes problems of reduction of conversion efficiency of a solar cell.
Several methods have been developed to obviate the aforementioned problems. One of the methods involves fabricating an insulating material between the adjacent regions of the backside electrode layer divided by pattern 1 (P1) to reduce the influence of leakage current on the shunt path (20c) (see, for example, Patent document 1.)
Other methods involve a process of expanding the width of pattern 1 (P1) to increase the distance between the regions of the backside electrode layer adjacent to pattern 1 (P1) thereby to reduce the influence of leakage current on the shunt path (20c).